Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the...Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the surface spin polarization of amorphous Co_(40)Fe_(40)B_(20)thin films with different annealing temperatures from 100℃to 500℃prepared by magnetron sputtering.After high annealing temperature,a quasi-semiconductor state is gradually formed at the CoFeB surface due to the boron diffusion.While the global magnetization remains almost constant,the secondary electrons’spin polarization,average valence band spin polarization and the spin polarization at Fermi level from spin-resolved photoemission spectroscopy show a general trend of decreasing with the increasing annealing temperature above 100℃.These distinct surface properties are attributed to the enhanced Fe-B bonding due to the boron segregation upon surface after annealing as confirmed by x-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy.Our findings provide insight into the surface spin-resolved electronic structure of the CoFeB thin films,which should be important for development of high-performance magnetic random-access memories.展开更多
We investigate the magnetic damping parameter of Fe 1−x Cr x thin films using the time-resolved magneto-optical Kerr effect technique.It is demonstrated that the overall effective damping parameter is enhanced with th...We investigate the magnetic damping parameter of Fe 1−x Cr x thin films using the time-resolved magneto-optical Kerr effect technique.It is demonstrated that the overall effective damping parameter is enhanced with the increasing Cr concentration.The effective damping at high fieldα0 is found to be significantly enhanced when increasing the Cr concentration with theα0=0.159 in the Fe 45 Cr 55 enhanced by 562%compared with that ofα0=0.024 in the pure Fe film.This study provides a new approach of controlling the effective damping parameter with a desired magnitude via varying Cr composition.展开更多
We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining...We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.展开更多
We investigate theoretically the spin accumulation in a Rashba spin-orbit coupling (SOC) nanoribbon nonadiabatically connected to a normal conductor.Both the nanoribbon and conductor are described by a hard-wall confi...We investigate theoretically the spin accumulation in a Rashba spin-orbit coupling (SOC) nanoribbon nonadiabatically connected to a normal conductor.Both the nanoribbon and conductor are described by a hard-wall confining potential.Using the scattering matrix approach within the effective free-electron approximation,we have calculated the out-of-plane spin accumulation in the nanoribbon.It is found that the spin accumulation shifts toward the two edges of nanoribbon with the increasing of propagation modes.Specifically,as the Rashba SOC strength increases the spin accumulation in the nanoribbon will be enhanced and this result may suggest us a simple method to control the spin accumulation of the system by Rashba SOC strength.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB3601600)the National Natural Science Foundation of China(Grant Nos.12104216,61427812,11774160,51971109,51871236,51771053,U1806219)+1 种基金the Natural Science Foundation of Jiangsu Province of China(Grant Nos.BK20200307,BK20192006,BK20180056)the Fundamental Research Funds for the Central Universities(Grant No.21014380113)。
文摘Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the surface spin polarization of amorphous Co_(40)Fe_(40)B_(20)thin films with different annealing temperatures from 100℃to 500℃prepared by magnetron sputtering.After high annealing temperature,a quasi-semiconductor state is gradually formed at the CoFeB surface due to the boron diffusion.While the global magnetization remains almost constant,the secondary electrons’spin polarization,average valence band spin polarization and the spin polarization at Fermi level from spin-resolved photoemission spectroscopy show a general trend of decreasing with the increasing annealing temperature above 100℃.These distinct surface properties are attributed to the enhanced Fe-B bonding due to the boron segregation upon surface after annealing as confirmed by x-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy.Our findings provide insight into the surface spin-resolved electronic structure of the CoFeB thin films,which should be important for development of high-performance magnetic random-access memories.
基金Supported by the National Key Research and Development Program of China(Grant No.2016YFA0300803)the National Natural Science Foundation of China(Grant Nos.61427812 and 11774160)+2 种基金the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20192006)the Fundamental Research Funds for the Central Universities(Grant No.021014380113)the Program for New Century Excellent Talents in Universities of Ministry of Education of China(Grant No.NCET-13-0094).
文摘We investigate the magnetic damping parameter of Fe 1−x Cr x thin films using the time-resolved magneto-optical Kerr effect technique.It is demonstrated that the overall effective damping parameter is enhanced with the increasing Cr concentration.The effective damping at high fieldα0 is found to be significantly enhanced when increasing the Cr concentration with theα0=0.159 in the Fe 45 Cr 55 enhanced by 562%compared with that ofα0=0.024 in the pure Fe film.This study provides a new approach of controlling the effective damping parameter with a desired magnitude via varying Cr composition.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20060542002the Hunan Provincial Natural Science Foundation of China under Grant No.06JJ2097the Hunan College of Science and Technology Research Foundation of China under Grant No.07XKYTB001
文摘We investigate theoretically the spin current in a quantum wire with weak Dresselhaus spin-orbit coupling connected to two normal conductors. Both the quantum wire and conductors are described by a hard-wall confining potential. Using the electron wave-functions in the quantum wire and a new definition of spin current, we have calculated the elements of linear spin current density j^Ts,xi and j^Ts,yi（i=x, y, z）. We find that the elements j^Ts,xx and j^Ts,yy have a antisymmetrical relation and the element j^Ts,yz has the same amount levelas j^Ts,xx and j^Ts,yy. We also find a net linear spin current density, which has peaks at the center of quantum wire. The net linear spin current can induce a linear electric field, which may imply a way of spin current detection.
基金Supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No.20060542002the Hunan Provincial Natural Science Foundation of China under Grant No.06JJ2097the Hunan University of Science and Engineering Research Foundation of China under Grant No.07XKYTB001
文摘We investigate theoretically the spin accumulation in a Rashba spin-orbit coupling (SOC) nanoribbon nonadiabatically connected to a normal conductor.Both the nanoribbon and conductor are described by a hard-wall confining potential.Using the scattering matrix approach within the effective free-electron approximation,we have calculated the out-of-plane spin accumulation in the nanoribbon.It is found that the spin accumulation shifts toward the two edges of nanoribbon with the increasing of propagation modes.Specifically,as the Rashba SOC strength increases the spin accumulation in the nanoribbon will be enhanced and this result may suggest us a simple method to control the spin accumulation of the system by Rashba SOC strength.
